The present invention relates to a hydraulic braking system, and more particularly to a hydraulic braking system having a braking circuit including a flow line, a brake circuit valve, a return line and at least one wheel brake, and in which the wheel brake is connectable alternatively to the flow line or to the return line by operation of the brake circuit valve.
A braking system of this type, having a second braking circuit added, is known, for example, from the WABCO brochure xe2x80x9cHydraulische Pumpenspeicher-Bremsanlagenxe2x80x9d of June 1995, as disclosed on page 12 thereof, and in its equivalent xe2x80x9cHPB Hydraulic Power Braking Systemxe2x80x9d of August 1996, on page 10 thereof, which are incorporated herein by reference. Such braking systems are normally used in wheel-borne devices, wherein the term xe2x80x9cwheel-borne devicesxe2x80x9d is understood to be all transportation, work and pulling machines, such as earth moving machines, loading machines, agricultural vehicles, rail vehicles, as well as road and off-the-road motor vehicles. Devices running on tracks, such as planing and loading caterpillars, are also considered to be wheel-borne devices, insofar as wheels thereof transmit the loads and the driving forces to the tracks.
Frequently, actuation of such a braking system independently of the brake valve may be required. Such a need arises, for example, when an excavator, a mobile crane or an agricultural tractor are used at a fixed location, or when a motor vehicle is to be equipped with a start-up slip control system and/or a travel dynamic control system.
It is therefore the object of the present invention to further develop a hydraulic braking system of the above-mentioned type in a simple manner, such that brake actuation independent of brake valve operation is made possible.
In accordance with these and other objects of the invention, there is provided a hydraulic braking system for a wheel-borne device which has a braking circuit including a flow line, a brake circuit valve, a return line and at least one wheel brake. The wheel brake is connectable alternatively to the flow line or to the return line by operation of the brake circuit valve. An electrically actuated valve system is further provided. When actuated, the electrically actuated valve system connects the wheel brake to the flow line parallel to the brake circuit valve and closes off the return line.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements and functions.